1. Field of the Invention
The present invention relates to an ink jet recording device for printing by ejecting ink droplets, and more particularly to a configuration for removing air bubbles from within ink channels running between an ink tank and a print head of the ink jet recording device.
2. Description of the Related Art
Ink jet recording devices print characters and other images by ejecting droplets of ink from a print head according to an inputted signal. Ink jet recording devices eject ink droplets by pressurizing ink in the print head using various types of actuators. For example, piezoelectric elements and electrode restrictive elements can be deformed according to the inputted signal to apply pressure to ink in the print head. Also, thermal elements can be energized according to the inputted signal to selectively generate heat to boil a portion of ink in the print head. The boiled ink forms expanding bubbles that increase pressure in the ink, thereby ejecting ink droplets.
The actuators are disposed in actuator chambers of the print head. Ink is supplied to the actuator chambers through a channel defined by side walls. Sometimes, for various reasons, air bubbles cling to the side walls of the ink channel. The air bubbles can enter actuator chambers where the actuators are located. Because the bulk modulus elasticity of air is extremely small compared to that of ink, the air bubbles in the actuator chambers absorb pressure generated by the actuator, so that pressure in the actuator chamber can not be properly increased. As a result, ink droplets can not be properly ejected. When ink droplets can not be properly ejected, print quality suffers greatly.
Japanese Patent-Application Publication (Kokai) No. SHO-56-75867 discloses a circulation purge operation for preventing air bubbles from entering actuator chambers. A circulation channel is provided between an ink tank and a manifold for distributing ink to actuators in the print head. The circulation channel includes a first channel for guiding ink from the ink tank to the manifold and a second channel for returning ink from the manifold to the ink tank. During the circulation purge operation, air bubbles clinging to the inner side walls and the like of the ink channels are removed by forcibly circulating ink through the circulation channel.